Cellulose esters containing succinyl groups and process of making same



' Patented Sept. 21', 1937 omonosn names comma succnm. onoors AND PBOCESSOEMAK- ING SAME Carl J. Malm, Rochester, N. Y.. and Charles E.

Waring, Dayton, Ohio, assignors, by mesne asslgnments, to Eastman Kodak Company, Jersey City, N. J., a corporation of New Jersey No Drawing. Application July 30, 1932, Serial No. 627.150

11 Claims. (Cl. 280-101) The present invention relates to the succinic acid esters of cellulose and the preparation of the same by reacting upon a cellulosic material with :uccinic anhydride in the presence of an organic ase.

This application is a continuation in part of our U. S. application Serial No. 380,252 flied July 22, 1929 in which there is described and claimed the preparation of dicarboxylic acid esters of cellulose by reacting upon cellulosic materials with the corresponding anhydride of the acid in the presence of an organic base.

In U. S. Patent No. 1,704,306 of Stinchfield is disclosed a process of preparing phthalyl containing cellulose esters. In that process one of the carboxyl groups of the phthalic acid must be esterified before the phthalic acid can be impelled into the cellulose. There is no disclosure in that patent of the preparation of succinic acid esters in any manner. There are other instances in the prior art of treatment of cellulose with phthalic compounds but nowhere have succlnates been described as being prepared. Whether or provide a process for producing succinic acid in which the esterification takes place in one step, I

esters of cellulose and more particularly a process thus eliminating the'necessity of preliminarily esterifying one of the carboxyl groups of the sucesters.

cinic acid before the esterification of the cellulosic material occurs. Another object of our invention is to produce a succinic acid ester of cellulose which is soluble in a number of the organic solvents commonly employed for dissolving and .preparing commercial products from cellulose Another object of our invention is to pro- 1videa process for the dope succinylation of cellu- 45 lose rather than the mere superficial succinylation Other objects will hereinafter .ganic base from which it can be later freed if desired by treating .the resulting compound with comparatively strong acid such as the mineral acids.

We have found that by reacting upon cellulose with a substantial amount of succinic anhydride in the presence of an organic base, that up to three molecules of succinic acid may combine with every (CtHmOa) group of the cellulose, which cellulose group will hereinafter be referred to as a unit of cellulose; We have found that by our process we obtain a succinic acid ester of cellulose in dope form, which is the usual formin Where the term celluiosic material is employed herein it is to be understood as including'both esterifiable celluloses such as cotton fibers and linters, paper or any customary types of purified cellulose and the esterifiable cellulose derivatives such as cellulose nitrates, ethers, acetates or acylates having free and esterifiable hydroxyl groups. v

The time of the succinylation of cellulosic material is governed to a great extent by the kind of cellulosic material used as the starting material.

For example. at a temperature of 60-65 C. ifunmodified cellulose is employed as the starting material, succinylation may take two or three weeks; while with a cellulose ether containing about ethoxy the time of succinylation may be cut down to about 24 hours. The time of suecinylation, however, also depends on otherfactors such for instance as the temperature. In our invention we have found it generally desirable to carry out the reaction at a temperature below approximately 110 C. but it will be understdod that higher or lower temperatures may be used. At the higher temperatures the succinylation will take place in much less. time; however, it is desirable that the temperature be kept sufflciently low to insure that a product will not be obtained; the properties of which have been markedly affected by the degradation of the cellulose.

When the required degree of esterification has occurred the succinic ester formed is precipitated by pouring the reaction mass into a dilute mineral acid solution or into an organic non-solvent for the ester such as an alcohol or an ether, for instance isopropyl ether, the latter having been disclosed and claimed in Malm and Fordyce application Serial No. 553,646, filed July 28, 1931.

The succinic esters which are obtained by the process of our invention are generally soluble in. various pyridine combinations such as pyridine and water, pyridine and benzene, pyridine and tetrachlorethane, pyridine and ethylene chloride, etc. Any of the latter three combinations may be employed in the succinylation process of curinvention instead of using pyridine entirely.

Various inert organic solvents may also be em-v ployed for dissolving the succinic esters, such as acetone, methyl alcohol-acetone, methyl acetate, ethyl acetate. ethylene chloride-methyl alcohol, propylene chloride-methyl alcohol, 1.4 dioxan, B.- methoxyethyl alcohol, ethylene glycol monoa'cetate, BBdichlorethyl ether-methyl alcohol. From a solution of a succinic ester of cellulose in one of the above-named solvents, a transparent sheet or skin may be formed by spreading the solution on a film-forming surface, such as a polished drum, and coagulated or solidified in a fluid stream of heated air or a non-solvent liquid. Various plasticizers such as methyl, ethyl or butyl phthalate, triphenyl or tricresyl phosphate, monochlornaphthalene, beta methoxyor beta ethoxyethyl phthalate or tributyl phosphate may be added to the solution prior to the formation of the skins or sheets. These succinic esters of cellulose may also be employed in adhesives, laminated glass. lacquers, artificial silk, molded products either alone or mixed with a plasticizer and other desired addition products. If a molded product is desired plasticizers such as B.methoxy ethyl phthalate which plasticizer is disclosed and claimed in Noller application Serial No. 504,640 filed December 24, 1930 or tributyl phosphate which plasticizer is disclosed and claimed in Smith application Serial No. 501,667 filed December 11, 1930 are eminently suited as agents of addition to the succinic esters especially the acetate-succinates as these plasticizers have been found to be solvents of those cellulose esters at elevated temperatures.

The following examples are illustrative of the carrying out of our invention:

Example I.5 gms. of cellulose such as tissue paper was treated with about 25 gms. of succinic 'anhydride in 75 cc. of pyridine at 60-65 C. the temperature being maintained constant by employing a jacketed container. In about a week a viscous dope was formed. This dope was precipitated in 5% hydrochloric acid and the precipitate was washed and dried. The cellulose succinate formed contained approximately 62% succinyl.

mesa-sea methyl alcohol (4:1). At elevated temperatures this cellulose acetate succinate was found to be soluble in the above solvents and also in methyl alcohol-acetone (2:1, 3: 1 and 4:1) ,bensene-methyl alcohol (1:1) and Bethany ethyl alcohol. As was pointed out above mixtures of pyridine with benzene, tetrachlorethane or ethylene chloride are solvents of the esters prepared by our invention, consequently a portion of the pyridine or the organic base employed in the esteriilcation bath may be replaced by one or more of these liquids.

Instead of pyridine .other organic bases. particularly of the tertiary variety may be employed in the process of our invention. In addition to pyridine other bases such as quinoline and alpha picoline have been found to be useful in the process of our invention. Other organic bases such as the dialkyl anilines for instance dimethyl aniline, the hexahydro-dialkyl anilines, dimethyl n-hexylamine and the like would at once suggest themselves to those skilled in the art, as a group which would supply organic bases suitable for employ-- ment as the acylating medium in the present invention.

In the process of our invention we have reason to believe that the succinic esters of cellulose prepared therein are combined with the organic base employed in the succlnylation. We believe that one of the carboxyl groups of the succinic acid is combined with the cellulose molecule, while the other carboxyl group is combined with the organic base, for example pyridine. While these esters containing Pyridine (or another base) in combination may have properties fitting them for particular uses, we find-it desirable to treat the succinic' esters. we obtain, with an excess of an acid which will free the succinic acid ester of cellulose from the combined pyridine. Although an organic acid such as acetic acid may be employed for this purpose, we prefer to employ a mineral acid. A common mineral acid such as sulfuric, hydrochloric, etc., is preferably employed.

The reactions which. are believed to take place in the process of our invention may be represented as follows:

Theoretically a fully esterifled cellulose trisuccihate contains 65% succinyl. "5 CHPC/ TAG Example II.10.grams of ordinary commercial acetone-soluble cellulose acetate containing approximately 39% acetyl, was dissolved in 55 cc. of 111-0 o c pyridine containing gms. of succinic anhydride 0 c and was maintained at a temperature of 60-65 arc-momma. C. in a jacketed kettle for about 4 days. 2 The AC --AC -Ac AO 0-c-cn, o +Hc1=-o-c-om o +(C;H N7H0l I Hs-C ()(ClHsNfil Hs-C-O ester was separated from the resulting dope by in which .precipitation in 5% hydrochloric acid and was I washed [with water and dried. The resulting lo compound, cellulose acetate-"succinate had a succinyl content of about 20%, a melting point of 232 C. and a precipitation value of 74%. It was found to be soluble at ordinary temperature in each of the following solvents; acetone, methyl alcohol-acetone (1:1), methyl or ethyl acetate, ethyl lactate, ethylene dichloride-methyl alcohol (4:1), propylene chloride-methyl alc hol (44 is employed to represent one unit of a partially de-esterified cellulose acetate based on Col-1100s as representing a unit of cellulose. Although the proportion of two acetyl groups to whereby a new compound can be made. For example the cellulose acetate-acid succinate may be treated with a base such as sodium, potassium or ammonium hydroxide or any of the organic bases above named and the reaction taking place in that case may be represented as follows:

in which R represents an organic or inorganic basic radical.

In the case of the sodium, potassium or ammonium salts of either the cellulose succinate or the acetate-succinate, the compounds are water-soluble.

Various other modifications of our invention will be apparent to those skilled in the art and also come within the scope of our invention. Where the term inert solvent is employed herein it refers to solvents such as benzene, tetrachlorethane and ethylene chloride which with pyridine will dissolve cellulose acetate-succinate.

We claim as our invention:

1. A process for preparing succinic acid esters of cellulose which comprises succinylating a cellulosic material with succinic anhydride in the presence of pyridine.

2. A process for preparing succinic acid esters of cellulose which comprises succinylating cellulose acetate containing esterifiable hydroxyl groups with succinic anhydride in the presence of a tertiary organic base.

3. A process for preparing cellulose acetatesuccinate which comprises treating a cellulose acetate with succinic anhydride, in the presence of pyridine.

4. A chemical compound represented by the formula in which hydrogen, acyl, alkyl, or

and R represents hydrogen or a basic substituent.

5. A chemical compound represented by the formula n-o-c in which represents a Cs unit of cellulose and X represents hydrogen, acyl, alkyl, or

ter of cellulose which comprises succinylating cellulose, with succinic anhydride in the presence of a tertiary organic base.

9. The process of making alkali-soluble succlnic acid esters of cellulose which comprises heating a compound containing the cellulose radical CeH-zOz and an OH group with succinic anhydride in the presence of a tertiary amine until the product is alkali-soluble.

10. An alkali-soluble succinlc acid-ester of cellulose.

11. A succinic acid ester of cellulose acetate.

CARL J. MAI-M. I CHARLES E. WARING. 

